Tyrosine kinases are a group of enzymes that specifically phosphorylate a tyrosine residue in proteins. The enzymes have a significant role in the intracellular signal transduction pathways and relate to a wide variety of biological functions including cell survival, differentiation, proliferation, and secretion. Janus Kinase (also referred to as JAK) family is known as that of intracellular tyrosine kinases involving a cytokine signaling. JAK family includes the four types of enzymes: JAK1, JAK2, JAK3 and Tyrosine Kinase 2 (also referred to as Tyk2). Once a cytokine associates with its respective cytokine receptor, JAK is phosphorylated, and a tyrosine residue of the receptor is then phosphorylated. Then, signal transducer and activator of transcription (also referred to as “STAT”), which exists in cells, will become associated with the phosphorylated tyrosine residue of the receptor, and a tyrosine residue of STAT is phosphorylated by JAK. The phosphorylated STATs form a dimer, and the dimer translocates into the nucleus and activates transcription of target gene, which leads to activation of the cells. JAK/STAT pathways are the key intracellular signal transduction pathways of cytokines in immunocompetent cells (Non-Patent Literature 1). About 40 types of cytokine signal transductions are mediated by a combination of the four JAKs and seven STATs, and abnormalities of a cytokine production and a cytokine signaling are believed to have an intimate involvement in not only various immune and inflammatory diseases, such as autoimmune diseases and allergic diseases, but also diseases having diverse pathologies such as cancers. Compounds suppressing the activation of these JAK/STAT pathways draw attention as new therapeutics for these diseases, and, in fact, JAK inhibitors have already been approved in the United States and Japan as a therapeutic for myelofibrosis, polycythemia vera and rheumatoid arthritis. Further, effects of such compounds are expected in the treatment of other autoimmune diseases (such as psoriatic arthritis, juvenile arthritis, Castleman's disease, systemic lupus erythematosus, Sjögren's syndrome, multiple sclerosis, inflammatory bowel disease, Behçet's disease, myasthenia gravis, type 1 diabetes mellitus, immunoglobulin nephropathy, autoimmune thyroid diseases, psoriasis, scleroderma, lupus nephritis, dry eye, vasculitis (such as Takayasu's arteritis, giant cell arteritis, microscopic polyangiitis, granulomatosis with polyangiitis and eosinophilic granulomatosis with polyangiitis), dermatomyositis, polymyositis and neuromyelitis optica), inflammatory diseases (such as atopic dermatitis, contact dermatitis, eczema, pruritus, food allergies, bronchial asthma, eosinophilic pneumonia, chronic obstructive pulmonary disease, allergic rhinitis, chronic sinusitis, eosinophilic sinusitis, nasal polyp, allergic conjunctivitis, osteoarthritis, ankylosing spondylitis, Kawasaki disease, Buerger's disease, polyarteritis nodosa and IgA vasculitis), proliferative diseases (such as solid cancers, blood cancers, lymph malignant tumor, myeloproliferative diseases, multiple myeloma, pulmonary fibrosis and eosinophilia), sudden hearing loss, diabetic nephropathy, alopecia areata, bone marrow transplant rejection or organ transplant rejection. Currently, the clinical trials are in progress for some diseases as listed above in Japan, the United States and Europe.
Specifically, various biological studies have demonstrated an important role of JAK1 in the signal transductions of many cytokines (See Non-Patent Literatures 2, 3 and 4), indicating that JAK1 inhibitors are useful in the treatment of the diseases, such as autoimmune diseases: psoriatic arthritis (See Non-Patent Literature 5), juvenile arthritis (See Non-Patent Literature 6), Castleman's disease (See Non-Patent Literature 6), systemic lupus erythematosus (See Non-Patent Literature 7), Sjögren's syndrome (See Non-Patent Literature 8), multiple sclerosis (See Non-Patent Literature 9), inflammatory bowel disease (See Non-Patent Literature 10), Behçet's disease (See Non-Patent Literature 11), myasthenia gravis (See Non-Patent Literature 12), type 1 diabetes mellitus (See Non-Patent Literature 9), immunoglobulin nephropathy (See Non-Patent Literature 13), autoimmune thyroid diseases (See Non-Patent Literature 14), psoriasis (See Non-Patent Literature 15), scleroderma (See Non-Patent Literature 16), lupus nephritis (See Non-Patent Literature 17), dry eye (See Non-Patent Literature 18), vasculitis (See Non-Patent Literatures 19, 20, 21, 22 and 23), dermatomyositis (See Non-Patent Literature 24), polymyositis (See Non-Patent Literature 24), neuromyelitis optica (See Non-Patent Literature 25); inflammatory diseases: atopic dermatitis (See Non-Patent Literature 26), contact dermatitis (See Non-Patent Literature 27), eczema (See Non-Patent Literature 28), pruritus (See Non-Patent Literature 29), food allergies (See Non-Patent Literature 30), bronchial asthma (See Non-Patent Literature 31), eosinophilic pneumonia (See Non-Patent Literature 32), chronic obstructive pulmonary disease (See Non-Patent Literature 33), allergic rhinitis (See Non-Patent Literature 31), chronic sinusitis (See Non-Patent Literature 34), eosinophilic sinusitis, nasal polyp (See Non-Patent Literature 35), allergic conjunctivitis (See Non-Patent Literature 36), osteoarthritis (See Non-Patent Literature 37), ankylosing spondylitis (See Non-Patent Literature 6), Kawasaki disease (See Non-Patent Literature 38), Buerger's disease (See Non-Patent Literature 39), polyarteritis nodosa (See Non-Patent Literature 40), IgA vasculitis (See Non-Patent Literature 41); proliferative diseases: solid cancers, blood cancers, lymph malignant tumor, myeloproliferative diseases, multiple myeloma (See Non-Patent Literatures 42, 43 and 44), sudden hearing loss (See Non-Patent Literature 45), diabetic nephropathy (See Non-Patent Literature 46), alopecia areata (See Non-Patent Literature 47), bone marrow transplant rejection or organ transplant rejection, etc. For example, the following clinical trials are in progress. Rheumatoid arthritis (https://clinicaltrials.gov/NCT01888874 and NCT02049138), Crohn's disease (https://clinicaltrials.gov/NCT02365649), non small cell lung cancer (https://clinicaltrials.gov/NCT02257619), pancreatic cancer (https://clinicaltrials.gov/NCT01858883), myelofibrosis (https://clinicaltrials.gov/NCT01633372) and psoriasis (https://clinicaltrials.gov/NCT02201524).
Further, among the cytokine signalings associated with JAK1, the inhibitors for the following cytokines have already been launched.    (1) IL-6 (also referred to as interleukin-6): therapeutic agents for rheumatoid arthritis, juvenile arthritis and Castleman's disease (See Non-Patent Literatures 48, 49 and 50).    (2) IL-2: therapeutic agent for acute rejection following renal transplantation (See Non-Patent Literature 51).
In addition, the clinical trials on the following cytokine inhibitors are in progress.    (3) IL-4 and IL-13: therapeutic agent for bronchial asthma, atopic dermatitis, eosinophilic sinusitis, nasal polyp and eosinophilic esophagitis (See Non-Patent Literature 31).    (4) IL-13: therapeutic agent for pulmonary fibrosis (See https://clinicaltrials.gov/NCT02036580).    (5) IL-5: therapeutic agent for bronchial asthma, chronic obstructive pulmonary disease, eosinophilia, eosinophilic granulomatosis with polyangiitis, eosinophilic esophagitis, eosinophilic sinusitis/nasal polyp and atopic dermatitis (See Non-Patent Literature 31 and Non-Patent Literature 52).    (6) IFNα (also referred to as interferon-α): therapeutic agent for systemic lupus erythematosus (See Non-Patent Literature 7).    (7) IL-31: therapeutic agent for atopic dermatitis (https://clinicaltrials.gov/NCT01986933).    (8) TSLP (also referred to as thymic stromal lymphopoietin): therapeutic agents for bronchial asthma (https://clinicaltrials.gov/NCT02054130) and atopic dermatitis (https://clinicaltrials.gov/NCT00757042).
Thus, the inhibition of JAK1 signal is a preferred means for the prevention or treatment of the diseases caused by an abnormality of JAK1, such as autoimmune diseases, inflammatory diseases and proliferative diseases.
As a JAK1 inhibitor, [1,2,4]triazolo[1,5-a]pyridines (See Patent Literatures 1 and 2), tricyclic pyrazinones (See Patent Literature 3), pyrrolopyrimidines (See Patent Literatures 4 to 7), phthalazines (See Patent Literature 8), imidazopyrrolopyridines (See Patent Literature 9 and Non-Patent Literature 53), diamino-1,2,4-triazoles (See Non-Patent Literature 54), pyrazolo[1,5-a]pyridines (See Patent Literature 10), imidazo[1,2-a]pyridines (See Patent Literatures 11 and 12), benzimidazoles (See Patent Literature 13), 7-azaindoles (See Patent Literature 14) are reported. However, none of the documents as mentioned disclose pyrazolo[5,1-b][1,3]thiazole compounds.